Y.-W. Bai and T.-H. Chen (Taiwan)
Real time clock, accuracy, CPLD, ppm.
Due to the importance of the accurate measurement of the real time clock (RTC) of high-end server systems such as multimedia server and video server systems during production, we propose the design and implementation of an automatic measurement system which is adjustable to measure the error of the real time clock. Our design uses a higher clock rate, like 10MHz, which provides a clock reference with a high resolution in comparison with the low clock rate of the real time clock of 32.768 KHz of the mainboard of a high-end server system. With the integration of the programming in a microprocessor, the modular CPLD design, the I/O and the interface circuits, we provide an inexpensive, accurate and easy to operate high-performance system for the RTC measurement in the high-end server systems on production lines. The measurement speed and the RTC accuracy are balanced to obtain high measurement efficiency for computer manufacturers. With this design the measurement time is adjusted and limited to within 20 seconds and RTC accuracy obtained to within ±0.1ppm, which betters our previous design whose accuracy stood at between ±11ppm and ±25ppm.
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